Dravet syndrome is a rare and catastrophic type of epilepsy in infants. Acute encephalopathy has been sporadically reported in patients with Dravet syndrome; however, the risk factors for this serious complication have not been identified. We report two patients with a clinical diagnosis of Dravet syndrome who experienced acute encephalopathy initiated by refractory status epilepticus. SCN1A mutational analysis revealed a previously reported nonsense mutation in one patient and a novel missense mutation in the other. Analysis of our cases and previously published cases revealed that patients with Dravet syndrome who have a more severe phenotype have an increased likelihood of developing acute encephalopathy compared with patients with less severe phenotypes.
Epilepsies, Myoclonic

BACKGROUND AND PURPOSE: Dravet syndrome is a rare and severe type of epilepsy in infants. The heterogeneity in the overall intellectual disability that these patients suffer from has been attributed to differences in genetic background and epilepsy severity. METHODS: Eighteen Vietnamese children diagnosed with Dravet syndrome were included in this study. SCN1A variants were screened by direct sequencing and multiplex ligation-dependent probe amplification. Adaptive functioning was assessed in all patients using the Vietnamese version of the Vineland Adaptive Behavior Scales, and the results were analyzed relative to the SCN1A variants and epilepsy severity. RESULTS: We identified 13 pathogenic or likely pathogenic variants, including 6 that have not been reported previously. We found no correlations between the presence or type of SCN1A variants and the level of adaptive functioning impairment or severity of epilepsy. Only two of nine patients aged at least 5 years had an adaptive functioning score higher than 50. Both of these patients had a low frequency of convulsive seizures and no history of status epilepticus or prolonged seizures. The remaining seven had very low adaptive functioning scores (39 or less) despite the variability in the severity of their epilepsy confirming the involvement of factors other than the severity of epilepsy in determining the developmental outcome. CONCLUSIONS: Our study expands the spectrum of known SCN1A variants and confirms the current understanding of the role of the genetic background and epilepsy severity in determining the developmental outcome of Dravet syndrome patients.
Adaptation, Psychological ; Asian Continental Ancestry Group* ; Child* ; Epilepsies, Myoclonic* ; Epilepsy ; Genetic Background ; Humans ; Infant ; Intellectual Disability ; Multiplex Polymerase Chain Reaction ; Population Characteristics ; Seizures ; Status Epilepticus ; Weights and Measures